The present invention relates to a double clutch for a hybrid drive of a motor vehicle. In addition, the present invention relates to a motor vehicle with such a double clutch.
In general, a hybrid vehicle is a vehicle that uses a plurality of energy sources, for example an internal combustion engine and an electric motor. In order to be able to achieve the highest possible energy efficiency, hybrid vehicles typically use so-called parallel hybrid drives, which enable the electric motor and the internal combustion engine to convey torque to a transmission not only alternatively, but also cumulatively. In contrast to a serial hybrid drive, wherein energy is converted first from the mechanical energy of the internal combustion engine into electric energy and then is used for operating the electric motor, a parallel hybrid drive does not always work at an optimal working point because the internal combustion engine and the electric motor are coupled together mechanically by a transmission. Therefore, the use of a double clutch transmission has been proposed in the past.
For example, DE 10 2004 062 530 A1 discloses such a double clutch transmission that is designed so that, in accordance with a respective operating state while achieving a high efficiency, the double clutch transmission can convey a torque from the electric motor and/or a torque from the internal combustion engine to the drive train.
An object of the present invention is to provide an improved double clutch that has, especially when used in a hybrid drive, a compact design.
The invention is based on the general idea of replacing two clutches that are usually arranged on the drive end and output end of the electric motor, with a commercially available double clutch in a parallel hybrid drive for a motor vehicle. Thereby, the overall length of the drive train is significantly shortened. In so doing, the double clutch that is used has an input shaft that can be driven by an internal combustion engine, and an output shaft that is connected to a transmission. In addition, there is an intermediate shaft that can be driven by an electric motor and extends coaxially to the output shaft. The input shaft and the intermediate shaft can be coupled together by a first clutch of the double clutch, whereas the intermediate shaft and the output shaft can be coupled together by a second clutch of the double clutch. At the same time, the electric motor is drive-connected directly to the intermediate shaft. Thus, individual operating states can be easily realized by an operating state-dependent opening or closing of the two clutches of the double clutch. For example, one can drive purely with the internal combustion engine, provided both clutches are closed, and the electric motor is not energized. In this state, the electric motor can act as the generator and charge up an energy accumulator. If no driving torque is supposed to be conveyed to the transmission, the second clutch can be opened; and the electric motor can be driven by the internal combustion engine over the closed first clutch and can be used for charging the energy accumulator. In a purely electric driving mode, however, only the second clutch is closed and the first clutch is opened so that the internal combustion engine is uncoupled from the electric motor. In a boost mode, both couplings are closed and both the electric motor and the internal combustion engine convey a torque to the transmission.
Expediently the output shaft extends coaxially through the electric motor. In this way an especially compact and constructionally space-minimizing configuration can be achieved, because, contrary to the prior art, the electric motor is arranged closely adjacent to the double clutch and is not installed apart from the double clutch as a result, of which additional torque transmitting elements would otherwise have to be provided. In particular, the close arrangement of the electric motor and clutch also reduces the weight, a feature that, in addition to the negligible constructional space requirement, is especially advantageous, in particular, in sports car construction.
Another advantageous embodiment of the present invention arranges the input shaft coaxially to the output shaft. The coaxial orientation of the input and output shaft offers the significant advantage that it is not necessary to redirect the power, for example with the aid of a cardan joint; and, as a result, only small transmission and/or translation losses occur.